GB2072480A - Method and apparatus for the salting of cheese curd - Google Patents

Abstract

A method of salting curd in the manufacture of cheese, in which milled curd on a moving conveyor 10 is sprayed with a liquid consisting of whey and salt through spray nozzles 13 while the curd is being agitated to distribute the liquid evenly throughout the curd. The salted whey is recycled. The recycled whey-salt liquid is filtered in filters 26 to remove fats and cheese fines, re-salted in container 20 and heated in heat exchanger 31 before being sprayed on curd. At periodic intervals the whey-salt liquid is heated to pasteurizing temperature. <IMAGE>

Description

SPECIFICATION Method and apparatus for the salting of cheese curd This invention relates to an improved method and apparatus for salting cheese curd.

Conventionally, in mechanised cheddar cheese making processes, dry salt (sodium chloride) is thrown or sprinkled over milled cheese curd moving on a conveyor. Thereafter this cheese curd requires a residence time before pressing (depending on the mellowing apparatus employed) from 10 minutes to 30 minutes, therefore extending the manufacturing time. In this method it is reasonably common for the concentration of salt absorbed by the milled curd to vary considerably from 1.5 to 2.5%. This variation of salt concentration allows taint producing bacteria to grow in regions of low salt concentration.

It has been proposed to salt milled curd by feeding the curd into a screw conveyor open at the top, and spraying brine, that is a water/salt solution onto the curd as it moves along the screw conveyor. This method would provide a more even distribution of salt in the curd, but has the disadvantage that the water washes out other valuable mineral salts from the cheese curd, resulting in a poorer quality cheese when mature, due to the imbalance between the mineral salt content of the water other than the sodium chloride content and the mineral salt content of the whey in the curd. This imbalance causes mineral salts to be transferred from the whey to the water by a solvent extraction or osmosis process.

The object of the invention is to provide an improved method and apparatus for obtaining a more uniform distribution of sodium chloride salt in milled curd, without any appreciable loss of other mineral salts from the curd.

According to the present invention there is provided a method of salting cheese curd comprising moving milled cheese curd through a treatment zone, spraying a liquid formed of cheese whey and salt onto the milled curd during its passage through the treatment zone, and draining the whey-salt liquid from the milled curd. The milled curd is preferably formed into a mat of curd on a moving drainage conveyor extending through the. treatment zone, and the milled curd agitated on the conveyor in the treatment zone to provide a substantially uniform distribution of the whey-salt liquid over the curd.

In the method of the invention, the use of whey as the liquid carrier for the salt minimises washing out of other mineral salts from the curd, since the liquid carrier of the salt has substantially the same composition as the whey in the curd and there is little or no imbalance between the mineral salt content of the two liquids, other than the sodium chloride content.

The method of the invention has the additional advantage over conventional dry salting processes that a commercial grade of salt can be used instead of the more expensive vacuum-dried salt which is required for a dry salting process. Also, the absence of salt dust in the atmosphere, as occurs with dry salting, reduces corrosion of the equipment.

The whey-salt liquid may be heated prior to contact with the cheese curd whereby the curd is heated to assist tn subsequent fusing together of the milled cheese curd. The heating means can conveniently be arranged to heat the whey-salt liquid to a pasteurising temperature, when not in use for salting, to kill any bacteria which may have developed in the whey.

Preferably the concentration of the salt in the whey is substantially at the saturation level thereof, that is, within the range of 20-25% salt concentration.

According to the invention there is also provided apparatus for salting milled curd in the manufacture of cheese, comprising a conveyor for moving the milled curd through a treatment zone, a reservoir for storing a liquid comprising cheese whey and salt, means for spraying liquid from said reservoir onto the milled curd on the conveyor as it passes through said treatment zone, means for agitating the milled curd to provide a substantially uniform distribution of the whey-salt liquid over the curd, means for draining the wheysalt liquid from the curd on the conveyor and returning the liquid to the reservoir, and means for heating the whey-salt liquid to a pasteurising temperature when not in use for salting curd.

The conveyor may be an endless conveyor of the slat type, the conveyor comprising a plurality of abutting and transversely extending slats of stainless steel capable of supporting the curd and permitting the excess wheysalt liquid to drain therethrough to be collected and recirculated. The means for agitating the curd may be rotary peg stirrers.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying schematic drawing.

The drawing illustrates an endless slat conveyor 10, a curd mill 11 (shown in block form) for cutting cheese curd into small pieces ready for salting, the curd mill 11 being arranged to deposit the milled curd onto one end of the conveyor 10, peg stirrers 1 2 for agitating milled curd on the conveyor, spray nozzles 1 3 for spraying whey into the milled curd, collecting trays 14 arranged underneath the conveyor to collect whey draining from the curd on the conveyor, and a whey recirculation and salting system arranged to feed whey from the trays 14 through filtration, salting and temperature controlling devices before returning the salted whey to the nozzles 13.

The conveyor 10 consists of thin stainless steel slats mounted at their ends on two endless drive chains respectively, the slats being spaced close together and presenting a substantially flat supporting surface for the curd but permitting whey to pass therethrough. The conveyor is fitted with fixed side skirts 1 5 for retaining the curd on the slats.

The peg stirrers 1 2 each comprise a power driven shaft which extends across the curd supporting surface of the conveyor, the shaft being fitted with a plurality of radially extend ing pegs which agitate the milled curd on the conveyor upon rotation of the shaft.

The spray nozzles 1 3 are connected in several rows extending across the curd supporting surface of the conveyor, the nozzles in each row being arranged so that salted whey is distributed substantially evenly across the full width of the curd supporting surface of the conveyor between the side skirts. The conveyor can conveniently be provided with two rows of nozzles for spraying the curd immediately upstream of the first peg stirrer and another two rows of nozzles for spraying the curd between the first and second peg stirrers, as shown in the drawing.

The whey re-circulation and salting system includes a tank 20 for storing a supply of whey, the tank 20 being fitted with a salt dozing device 21 and a stirrer 22. A pump 23 is arranged to draw whey through a line 24 from the collection trays 14 and feed the whey through line 25, a filter 26 and line 27 into the tank 20. A positive displacement pump 28 is arranged to draw salted whey from the tank 20 and feed the whey through a filter 30, a heat exchanger 31, and through line 32 to the nozzles 1 3. A reserve tank 33 is connected to line 25 through a valve 34 to provide a reservoir for the whey when the remainder of the system is being cleaned. A pump 35 is operable to feed whey from the tank 33 through line 36 into the tank 20.

The tank 20 is provided with a partition 40 extending downwards from the roof of the tank and a further partition 41 extending upwards from the floor of the tank, the partitions subdividing the tank into an inlet compartment 42, a central compartment 43 and an outlet compartment 44. The lines 27, 36 open into the inlet compartment 42, and the pump 28 draws salted whey from the outlet compartment 44 through line 32.

The salt dozing system comprises a hopper 46 for storing dry salt, a feed screw 47 extending through the hopper into an outlet pipe 48 leading into the inlet compartment 42 of the tank, and a motor 49 for driving the screw. The stirrer 22 is mounted in the central compartment 43 of the tank and is driven by a motor 50.

The heat exchanger 31 is adapted to heat or cool the whey to keep it within desired temperature limits. The heat exchanger is also adapted to heat the whey to pasteurizing temperature at periodic intervals to sterilize the whey.

In use, the curd mill 11 feeds milled curd continuously onto the conveyor 10 which is driven at constant speed. Whey saturated with salt is sprayed through the nozzles 1 3 onto the curd on the conveyor, and the peg stirrers 12 are driven so as to agitate the curd and distribute the salted whey substantially evenly throughout the curd. The whey drains through the conveyor into the trays 14 from which it is returned to the tank 20. The whey is obtained initially from the earlier stages of manufacture of the cheese.

The whey is maintained by the heat ex changer 31 at a temperature dependent upon the type of cheese being manufactured, the whey in turn heating the cheese curd which assists in the subsequent fusing together of the curd pieces when they are pressed in a mould to form a block of natural cheese for maturing in store.

The whey draining from the curd tends to carry away fats and cheese fines from the curd, but most of these fats and cheese fines are removed by the filter 26. The fats and cheese fines are generally lighter than the whey-salt liquid and any which remain in the liquid will float to the surface of the inlet compartment 42 of the tank 20 when the liquid is pumped into the tank, and can be periodically skimmed off or removed by any other suitable means. The whey-salt liquid, substantially devoid of lighter contaminants such as fats and cheese fines, flows from the inlet compartment 42 underneath the baffle 40 into the central compartment 43.

The make-up salt supplied by the salt doz ing system to the liquid in the inlet compart ment 42 may consist of a relatively coarse variety which can include some sand. This sand being heavier than the whey-salt liquid tends to settle in the central compartment 43 towards the base of the tank 20 where it can be removed via outlet 51. Any other contami nants heavier than the whey-salt liquid may be removed in a similar manner. The liquid in the central compartment is agitated by the motor-driven stirrer 22 to expedite the d!ssolv- ing of the salt in the whey. Whey-salt liquid, free of most contaminants, flows from the central compartment 43 over the baffle 41 into the outlet compartment 44. A second heavy solids outlet 52 is provided in the base of the outlet compartment to allow any further solids settling out to be removed. The outlet 52 is located at a distance substantially below the outlet for line 32.

The conveyor 10 is provided with a variable speed drive whereby the length of time the milled curd spends in the treatment zone may be varied, and the number of spray nozzles in operation may be controlled by valves. The rate and quantity of salt absorption may then be adjusted by varying the number of operative spray nozzles and the speed of the conveyor. Sensor means may be provided for testing the condition of the excess liquid in each of the individual collection trays 1 4 and this information may be used to control the various operating parameters.

When the apparatus is closed down after completing the salting of a batch of curd, the whey-salt liquid is heated in the heat exchanger 31 to pasteurising temperature and stored in the tank 33 while the remainder of the system is being cleaned.

Claims (11)

1. A method of salting cheese curd comprising moving milled cheese curd through a treatment zone, spraying a liquid formed of cheese whey and salt onto the milled curd during its passage through the treatment zone, and draining the whey-salt liquid from the milled curd.

2. A method as claimed in claim 1, including forming the milled curd into a mat of curd on a moving drainage conveyor extending through said treatment zone, and agitating the milled curd on the conveyor in said treatment zone to provide a substantially uniform distribution of the whey-salt liquid over the curd.

3. A method as claimed in claim 1 or 2, wherein the whey-salt liquid is heated prior to contact with the curd whereby the curd is heated to assist in the subsequent fusing together of the milled cheese curd.

4. A method as claimed in claim 1 or 2, wherein the whey-salt liquid is heated to pasteurising temperature and then cooled prior to being sprayed onto the milled curd.

5. A method as claimed in any of claims 1-4, wherein the salt in the whey is within the range 20-25% salt concentration.

6. A method as claimed in any of claims 1-5, wherein the drained whey-salt liquid is filtered to remove fats and cheese fines, resalted, and sprayed onto a subsequent batch of milled curd.

7. A method as claimed in claim 6, wherein the drained whey-salt liquid is fed into a first zone of a reservoir in which contaminants lighter than the liquid are allowed to rise to the upper levels of the first zone, and the Jiquid is thereafter fed into a second zone in which contaminants heavier than the liquid are allowed to settle to the bottom of the second zone.

8. A method as claimed in claim 2, comprising regulating the speed of the conveyor so as to control the residence time of the curd in said treatment zone.

9. Apparatus for salting milled cheese curd in the manufacture of cheese, comprising a conveyor for moving the milled curd through a treatment zone, a reservoir for storing a liquid comprising cheese whey and salt, means for spraying liquid from said reservoir onto the milled curd on the conveyor as it passes through said treatment zone, means for agitating the milled curd to provide a substantially uniform distribution of the wheysalt liquid over the curd, means for draining they whey-salt liquid from the curd on the conveyor and returning the liquid to the reservoir, and means for heating the whey-salt liquid to a pasteurizing temperature when not in use for salting curd.

1 0. Apparatus as claimed in claim 9 wherein the reservoir is provided with baffle means driving the reservoir into a first zone in which contaminants in the whey-salt liquid lighter than the liquid can rise to the upper levels of the first zone for removal therefrom, and a second zone in which contaminants in the whey-salt liquid heavier than the liquid can settle to the bottom of the second zone for removal therefrom the second zone communicating with the first zone only in the bottom portion of the reservoir.

11. A method of salting milled cheese curd as claimed in claim 1 and substantially as hereinbefore described with reference to the accompanying drawing.

1 2. Apparatus for salting milled cheese curd substantially as hereinbefore described with reference to the accompanying drawing.